Moving towards a novel therapeutic strategy for hyperammonemia that targets glutamine metabolism
Moving towards a novel therapeutic strategy for hyperammonemia that targets glutamine metabolism
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DOI：
10.1002/jimd.12540
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发表时间：
2022-08-04
影响因子：
4.2
通讯作者：
Yoshino, Makoto
中科院分区：
文献类型：
--
作者：
Fukui, Kaori;Takahashi, Tomoyuki;Yoshino, Makoto
尿素循环障碍的患者间歇性地出现高氨血症失代偿发作。虽然这种情况通常与饥饿和分解代谢有关，但其分子基础尚不完全清楚。首先，我们试图阐明这种饥饿相关的高氨血症的机制。利用小鼠胚胎成纤维细胞(MEF)培养系统，我们发现葡萄糖饥饿增加了氨的产生，并且这种增加与谷氨酰胺分解的增强有关。这些结果使我们关注谷氨酸脱氢酶抑制剂α-酮戊二酸(AKG)，以及一种主要的抗性激素代谢产物。因此，我们试图确定α-酮戊二酸二甲酯(DKG)(一种细胞通透性AKG类似物)对MEF的影响，发现DKG主要通过谷氨酸脱氢酶减少通量来减少氨的产生。我们还验证了DKG在NH4Cl激发的高氨血症小鼠模型中降低氨的作用，并观察到DKG给药将血氨浓度降低到只服用NH4Cl的对照小鼠平均值的22.8%。此外，在DKG治疗后，我们检测到Omitine浓度和Omitine/Arg比率的增加。我们随后给一只因鸟氨酸转氨酶缺乏而导致高氨血症的新生猪静脉注射DKG，发现血氨浓度随着时间的推移而显着下降。我们确定这种作用与促进还原氨化和谷氨酰胺合成有关。我们目前的数据表明，能量饥饿通过增强谷氨酰胺分解来触发高氨血症，而DKG在体外和体内都通过多效性机制减少氨蓄积。因此，细胞透性的AKG是一种新的高氨血症治疗的可行候选药物。
Patients with urea cycle disorders intermittently develop episodes of decompensation with hyperammonemia. Although such an episode is often associated with starvation and catabolism, its molecular basis is not fully understood. First, we attempted to elucidate the mechanism of such starvation-associated hyperammonemia. Using a mouse embryonic fibroblast (MEF) culture system, we found that glucose starvation increases ammonia production, and that this increase is associated with enhanced glutaminolysis. These results led us to focus on alpha-ketoglutarate (AKG), a glutamate dehydrogenase inhibitor, and a major anaplerotic metabolite. Hence, we sought to determine the effect of dimethyl alpha-ketoglutarate (DKG), a cell-permeable AKG analog, on MEFs and found that DKG mitigates ammonia production primarily by reducing flux through glutamate dehydrogenase. We also verified that DKG reduces ammonia in an NH4Cl-challenged hyperammonemia mouse model and observed that DKG administration reduces plasma ammonia concentration to 22.8% of the mean value for control mice that received only NH4Cl. In addition, we detected increases in omithine concentration and in the ratio of omithine to arginine following DKG treatment. We subsequently administered DKG intravenously to a newborn pig with hyperammonemia due to ornithine transcarbamylase deficiency and found that blood ammonia concentration declined significantly over time. We determined that this effect is associated with facilitated reductive amination and glutamine synthesis. Our present data indicate that energy starvation triggers hyperammonemia through enhanced glutaminolysis and that DKG reduces ammonia accumulation via pleiotropic mechanisms both in vitro and in vivo. Thus, cell-permeable forms of AKG are feasible candidates for a novel hyperammonemia treatment.